Institutional investment managers must disclose their quarterly portfolio holdings in a Form 13F. The 13(f) rule allows the SEC to delay disclosure that is “necessary or appropriate in the public interest or for the protection of investors.” When filers request confidential treatment for certain holdings, they may omit those holdings off their Form 13F. After the confidentiality period expires, the filer must reveal the holdings by filing an amendment to the original Form 13F.

Confidential treatment allows hedge funds to accumulate larger positions in stocks, and to spread the trades over a longer period of time. Funds request confidentiality where timely disclosure of portfolio holdings may reveal information about proprietary investment strategies that other investors can free-ride on without incurring the costs of research. The Form 13F filings of investors with the best track records are followed by many investors. Warren Buffett’s new holdings are so closely followed that he regularly requests confidential treatment on his larger investments.

Hedge funds seek confidentiality more frequently than other institutional investors. They constitute about 30 percent of all institutions, but account for 56 percent of all the confidential filings. Hedge funds on average relegate about one-third of their total portfolio values into confidentiality, while the same figure is one-fifth for investment companies/advisors and one-tenth for banks and insurance companies.

The authors make three important findings:

Hedge funds with characteristics associated with more active portfolio management, such as those managing large and concentrated portfolios, and adopting non-standard investment strategies (i.e., higher idiosyncratic risk), are more likely to request confidentiality.

The confidential holdings are more likely to consist of stocks associated with information-sensitive events such as mergers and acquisitions, and stocks subject to greater information asymmetry, i.e., those with smaller market capitalization and fewer analysts following.

Confidential holdings of hedge funds exhibit significantly higher abnormal performance compared to their original holdings for different horizons ranging from 2 months to 12 months. For example, the difference over the 12-month horizon ranges from 5.2% to 7.5% on an annualized basis.